请问下面这段代码在DFT中reset_n端报错要怎么解决

rr43578i

always @ (posedge clk)

if (reset_n == 0)

run_before <= 0;

else if (cavlc_decoder_state == `run_before_LUT)

case (zerosLeft)

0:run_before <= 0;//special case added for "total_zeros==0"

1:run_before <= (BitStream_buffer_output[15] == 0)? 4'd1:4'd0;

2:if      (BitStream_buffer_output[15] == 1)        run_before <= 0;


  else if (BitStream_buffer_output[15:14] == 2'b01)
run_before <= 1;

  else                                              run_before <= 2;


3:case (BitStream_buffer_output[15:14])

2'b00:run_before <= 3;

2'b01:run_before <= 2;

2'b10:run_before <= 1;

2'b11:run_before <= 0;

  endcase

4:case (BitStream_buffer_output[15:14])

2'b00:run_before <= (BitStream_buffer_output[13] == 1)? 4'd3:4'd4;

2'b01:run_before <= 2;

2'b10:run_before <= 1;

2'b11:run_before <= 0;

  endcase

5:case (BitStream_buffer_output[15:14])

2'b00:run_before <= (BitStream_buffer_output[13] == 1)? 4'd4:4'd5;

2'b01:run_before <= (BitStream_buffer_output[13] == 1)? 4'd2:4'd3;

2'b10:run_before <= 1;

2'b11:run_before <= 0;

  endcase

6:casex (BitStream_buffer_output[15:13])

3'b11x:run_before <= 0;

3'b000:run_before <= 1;

3'b001:run_before <= 2;

3'b011:run_before <= 3;

3'b010:run_before <= 4;

3'b101:run_before <= 5;

3'b100:run_before <= 6;

  endcase

default:

case (BitStream_buffer_output[15:13])

3'b000:run_before <= run_of_zeros_len + 3;

3'b111:run_before <= 0;

3'b110:run_before <= 1;

3'b101:run_before <= 2;

3'b100:run_before <= 3;

3'b011:run_before <= 4;

3'b010:run_before <= 5;

3'b001:run_before <= 6;

endcase

endcase